1. Field of the Invention
The present invention relates to a magnetism detecting device and an electronic azimuth meter using the same.
2. Description of the Related Art
When an azimuth is electronically measured, a magnetometric sensor that detects geomagnetism is used. In order to calculate an azimuth by use of a magnetism detecting device having such a magnetometric sensor, a technology has been known in which an alternating current (AC) bias magnetic field is applied to the magnetometric sensor and a voltage outputted from the magnetometric sensor is measured when the bias magnetic field of each polarity is applied thereto. Then, the voltage value is stored in a capacitor, and an azimuth is calculated by use of the difference between the voltage values of the respective polarities. Accordingly, errors due to offset characteristics and hysteresis characteristics peculiar to the magnetometric sensor can be eliminated.
However, in the above-described magnetism detecting device, a voltage difference value outputted from an amplifier in a circuit inevitably includes an offset voltage peculiar to the amplifier, which causes an azimuth error. Generally, the offset voltage is several mV, and the azimuth is deviated by 5° to 10° due to the offset voltage.